In display systems, such as those involving liquid crystal or plasma displays, the use of multiple video lines for signal transmission often produces a periodic intensity variation known as a corduroy effect. The corduroy effect is a result of mismatches among the analog portion of parallel video paths such as the digital-to-analog converters and operational amplifiers. If the multiple video inputs are not balanced (that is, if the equal levels of video signals are not matched among different inputs) a periodic effect will appear in the displayed image. If the multiple video inputs are used to provide the video signal to interleaved sets of columns, a periodic intensity variation (“corduroy” pattern) among columns will appear, especially in the regions where the image contains features with uniform color or shades. If the multiple video inputs are used to provide the video signal to interleaved rows, the periodic effect will appear in the rows of the image.
Mismatches occur along paths with analog components due to a variety of factors. Analog circuit components have inherent differences in device characteristics, such as component tolerances which produce differences in gain and offset. Also, analog circuit components suffer performance degradation over time at varying rates, producing further differences among device components.
One existing method of overcoming the mismatches among analog components is to manually adjust device characteristics such as operational amplifier gain and offset among video paths using a device such as a potentiometer. However, the cost and labor required to tune device characteristics such as gain and offset of multiple components is not desirable in a high volume production environment. Therefore, the complications of balancing multiple video signals to minimize corduroy is costly, time consuming, and difficult.